Many popular Kotlin libraries are preinstalled and readily available (see the list of supported Kotlin libraries). We can see that run accepts a return statement whereas “apply” does not accept a return statement(we can see the error thrown by the IDE in the image) and always returns the same object which it is referring to. The way to refer to the context object 2. JVM. “the tldr; on Kotlin’s let, apply, also, with and run functions” is published by Andre Perkins in ProAndroidDev. Supported and developed by JetBrains. Hence, by using the also operator, the code can be modified as: This way we can execute the intermediate result within the execution chain without breaking the chain, thereby leading to a better readable code. Subtle differences between Kotlin's with(), apply(), let(), also(), and run() June 3, 2017 in programming. The difference is run refers to the context of the object as “this” and not “it”. fun returns “Result” — let, run, with when we use the above functions, you can use the object within the block and returns whatever the last line of the block gives as a result. If you have enough hands-on experience, you might be already using scope functions. In this case, you would probably prefer the top row - either let() or also(). Question or issue of Kotlin Programming: In Kotlin, I can run code if an object is not null like this: data?.let { ... // execute this block if not null } but how can I execute a block of code if the object is null? a block of code, in the context of an object. I think it might be of help to other people also, so here it is: So let’s say if we modify the function as: We can see that since there was no return value in the let block and hence printing the same would indicate that the “print” functionality is called upon a unit function. It also refers to the context of the object as “this”, similar to how the “run” operator uses it. Using them can increase readability and make your code more concise. Now, let us run the Android Application, and see how the tint color affected the ImageView. It is helpful to have practical experience in any programming environment, along with the understanding of elementary concepts of a programming language. The return value. With the help of these functions (let, run, with, apply and also),we can operate on objects within a certain context. One of the small but loved is the scoped functions. In Datalore notebook you can run Kotlin code directly in your browser. Build final native binaries. The Kotlin standard library offers four different types of scope functions which can be categorized by the way they refer to the context object … But with run(), the result returned is the result of the code block, so we’d shuffle that call to get(): These two dimensions - context and result - can form a nice little grid that can make it easy to remember what’s what: Following the first letter of each, you get the acronym “LARA”. This implies that the “let” operator provides an option to perform an operation on the current object and return any value based on the use case. Code written sequentially is typically easier to read, and can even use language features such as exceptions. So if run is similar to let in terms of accepting any return value, what’s the difference? If so, you’ll want one of the functions on the right-hand column, because they return the receiver object when you’re done. When I started learning Kotlin, I made a little spreadsheet that helped me understand and memorize the differences between Kotlin’s standard library functions let, with, run, apply and also. Hence, a “run” operator can be used to initialize an object and return the result of it. We can also represent the summary of choosing between the scoped functions as a flowchart. We will be discussing the following topics in this article: Well, what does this mean? Kotlin coroutines let you convert callback-based code to sequential code. Publish a multiplatform library. We have many scenarios where we should return an instance of Intent or an Alert Dialog etc., by adding specific attributes to them. Kotlin let let takes the object it is invoked upon as the parameter and returns the result of the lambda expression. These functions provide a way to give temporary scope to the object under consideration where specific operations can be applied to the object within the block of code, thereby, resulting in a clean and concise code. As a starting point for examination, let’s look at some code. Kotlin has some really cool extension functions as part of the Standard library. I think it might be of help to other people also, so here it is: They are scoping functions that take a receiver argument and a block of code, and then execute the provided block of code on the provided receiver. Although whatever you do with scope functions can be done without, they enable you to structure your code differently. Common. So let’s see the difference between apply and run functions. One special collection of relevant functions can be described as "scope functions" and they are part of the Kotlin standard library: let, run, also, apply and with. 07/09/19 by Frank Rosner . Build final native binaries. Let’s consider a case where a Person object can be nullable. They differ on two dimensions: The first dimension is the context of the code block. Because the scope functions are all quite similar in nature, it's important to understand the differences between them. Compare the two EditText objects being created in this code listing. a block of code, in the context of an object. In Kotlin, if the last statement in a “let” block is a non-assignment statement, it is by default a return statement. Kotlin let is a scoping function wherein the variables declared inside the expression cannot be used outside. Functions in Kotlin are very important and it's much fun () to use them. let. Kotlin and Java EE: Part One - From Java to Kotlin One of the main strengths of Kotlin is good Java integration. ... Kotlin™ is protected under the Kotlin Foundation and licensed under the Apache 2 license. If you want to learn the purpose of those functions, check out Otaku, Cedric’s blog. The second dimension is the return value. .also () .let () .apply () .run () They are magical because they can perform some Kotlin magics and at the same time greatly resemble English words. The advantage of using “also” operator is that while doing a chain of operations, this operator helps in evaluating the current operating value if required. So apply() fits in the first category - it returns the receiver object. 1. let and run transform 1a. It refers to the context of the object by using the “it” keyword and hence, this “it” can be renamed to a readable lambda parameter. A coroutine is a concurrency design pattern that you can use on Android to simplify code that executes asynchronously.Coroutines were added to Kotlin in version 1.3 and are based on established concepts from other languages.. On Android, coroutines help to manage long-running tasks that might otherwise block the main thread and cause your app to become unresponsive. So apply() falls under the second case - this refers to the Calendar instance. Native. Yeah. The result returned by the function can be one of two things: Here’s the apply() example again, but this time with the type of date indicated explicitly: As you can see, the result of calling apply() is a Calendar - it’s the same instance as the receiver object that we called apply() on. Let’s go through them one by one. No Comments . Here’s how you’d include the latest version of Kotlin in your project-level build.gradle file: Let’s also apply run with Kotlin scope functions. Pixtory App (Alpha) - easily organize photos on your phone into a blog. In Software Development, things are only better understood by implementing rather than reading. Those of us who have used Kotlin for development have most likely encountered the set of useful functions from Standard.kt. ... Kotlin™ is protected under the Kotlin Foundation and licensed under the Apache 2 license. There are five of them: let, run, with, apply, and also. In this guide, we’re going to clarify four of these scope functions in particular - let(), also(), run(), and apply().By the end of this guide, you’ll have a framework for … So let's forget about it also let apply run for a second. Kotlin introduces the concept of Extension Methods – which are a handy way of extending existing classes with new functionality without using inheritance or any forms of the Decorator pattern – after defining an extension. pug analogy, part I There's a famous saying "to begin learning is to begin to forget". Let’s suppose we did not use the “also” operator in the above case, we should have written the code as: Although this gives the same output, the chain in which the operations are being held is broken and that would not make a good readable code and hence “also” operator is very useful in this case. You probably have seen some of them in various tutorials or even used them already. Let’s say we make the “. Scope functions. But have you ever been confused like all of them seem the same? So depending on the use case and requirement we have to choose between the let and the run operator. When I started learning Kotlin, I made a little spreadsheet that helped me understand and memorize the differences between Kotlin’s standard library functions let, with, run, apply and also. Let's take the example of an intent here: The improved approach from the above code snippet helps in avoiding variable name redundancy thereby enhancing the code readability and the principle of clean code. Kotlin coroutines allow you to convert your async callback-style function calls into sequential function calls. 1.0. On the other hand, if your code block is calling lots of functions on the receiver, you get better signal-to-noise ratio by using one of the two functions from the bottom row - either run() or apply(), because you won’t need to specify the object at all. Native. Let's say you have a pug. If you read some Kotlin code before you probably already seen them. Supported and developed by JetBrains. and you want to add a horn to it. we can essentially use it – as it was part of the original API.. So let’s see the difference between also and let functions. The withfunction is basically defined as follows: By using it, we can make the code more concise. The also, apply, let, run, and with functions, when used properly in Kotlin, make your code more readable. Run tests. If you have a device connected and you’ve set it up for development, then it’ll show up here and you can click OK and it’ll run on your device. From the above code snippet, we can see that although “let” operation is performed on a Person object, the output of the code is a string value and not the Person object. There are five scoped functions in Kotlin: let, run, with, also and apply. In Kotlin, scope functions allow you to execute a function, i.e. This guide will show when and when not to use them. 暖心芽 (WIP) ️ - reminder of hope, warmth, thoughts and feelings. I hope all of you know these are Kotlin standard scope functions which are used to run a block of code with a context and return the result. The “run” operator also helps in easy null checks similar to the “let” operator. Let’s see the same example, but this time using also(): This time, since we’re using also() instead of apply(), we had to prefix the set() calls with it. Nice! What is the importance of each scoped function? Since we had to print the result we stored the result in a separate variable and then printed it. ... For having additional effects or grouping function calls on an object use let, run, with. ... kotlin-stdlib / kotlin / let. Let’s see some ordinary code that does not use scoping functions, first: The following code snippet is equivalent to the one above, except that it uses with() sco… The “with” operator is completely similar to the run operator that we just discussed. It also comes with an efficient way of working with background threads, main threads, and dedicated I/O threads. By the end of this guide, you’ll have a framework for understanding them and should have a good idea of which one is most applicable in different scenarios. How should we choose between these two? let is one of Kotlin's Scope functions which allow you to execute a code block within the context of an object. Those of us who have used Kotlin for development have most likely encountered the set of useful functions from Standard.kt. Their usages range from but are not exclusive to initialization and mapping. COVID-19 - data, chart, information & news. So if you’ve been using any version of Kotlin that’s below 1.3.0, it’s recommended that you upgrade the version in Android Studio IDE. Kotlin defines a few of extension functions like with() and apply() in its Standard.kt file. JS. One point here is that since the context is referred to as “this”, it cannot be renamed to a readable lambda parameter. Now, this is an interesting case. Here's the code for doing this. 暖心芽 (WIP) ️ - reminder of hope, warmth, thoughts and feelings. That includes me. Pixtory App (Alpha) - easily organize photos on your phone into a blog. In our example above, the receiver is an instance of Calendar - the instance that was returned by getInstance(). “let” can also be used when we want to perform an operation on the result of a call chain. You probably have seen some of them in various tutorials or even used them already. 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